The present invention pertains to an improved process for preparing relatively high molecular weight epoxy resins by advancing relatively low molecular weight epoxy resins with a polyhydric phenol.
One method for preparing relatively high molecular weight epoxy resins is to react a relatively low molecular weight epoxy resin with a polyhydric phenol. The relatively low molecular weight epoxy resin usually contains a small quantity of hydrolyzable halide. During the advancement reaction, an increase in hydrolyzable halide content is observed. Also noticed is that the epoxide equivalent weight of the advanced epoxy resin tends to increase while the advanced epoxy resin is being held at elevated temperatures awaiting further processing such as, for example, flaking and/or transfer to storage vessels and the like.
The present invention tends to eliminate or reduce the increase in hydrolyzable halide content during the advancement reaction and/or reduce the increase in epoxide equivalent weight (EEW) of the resultant advanced epoxy resin held at elevated temperature while awaiting further processing.